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An important facility for 9th class students preparing for short questions physics 9th class chapter 6 of BISE. Get hundreds of questions to prepare and get better marks in 9th physics
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Question: 1
Define work and explain how work is calculted if force .Write Mathematically .
Answer: 1
1-26
Work: Work is said to be done when a force displaces a body in its own direction.
Explain: In our daily life, when somene hold a body in state of rest no work id done because it does not cover any displacement, In the scientific sense, work is said to be done, when a force acts on a body there must be motion or displacementby a body in the direction of the force.
Mathematically:
Work = fore x displacment.
or
W = FS
Unit of work:
Work done is a scalar quantity and the SI unit of work is Joule ,denoted by 'J' and canbe defined as.
W= Fs
so, 1J = 1N , 1M
Or, 1 J = 1 Nm
Question: 2
Write Mass Energy Equation.
Answer: 2
2-26
According to Einstein's mass energy equation "The energy "E" of a physical system is numerically equal to the product of its mass \m\ and the speed of light \c\ squared. It is also known as mass energy equivalence.
Mathematical form: Energy = mass x the speed of light squared
E = m x c2
E= mc2
There the speed of light is constant having value of 3 x108ms-1, however gthis value needs to be squared.
This dquation shows the relationship between mass and energy gthat mass and energy are same physical entities and can be changed into each other.
Question: 3
Define Wind Energy
Answer: 3
3-26
The Kinetic energy of the wind is currently used in many parts of the world to generate electricity. It is a renewable resource that can be used again and again. It is ecofriendly source of energy but require very large open space.
Question: 4
What is Gravitational potential Energy.
Answer: 4
4-26
When a body is taken to a height with respect to earth, here work is done against the force of gravity then potential energy stored in a body will be termed as gravitational potential energy, It is denoted by " EGp.E" If we relese the body from that height. It will accelerate and gain kinetic energy as its velocity increase. Thys "EG.P.E. can be relesed and have the ability to do useful work.
Mathematical form:
Mathematically, gravitational potential energy is the product of mass'm', the acceleratio due to gravity 'g' and the change in height 'h'
Question: 5
Define major sources of energy Fossil Fuels
Answer: 5
5-26
Coal, oil and natural gas are called fossile fuels because they are non-renewable resources that formed when prehistoric plants and animals died and were gradually buried by layers of rock. Over million of years, different types of fossil fuels -i-e coal, oil or gas are formed.
Coal is most abundant fossil fuel in world, with an estimated reserve of on million metric tons.
Crude oil is refined into many different types of energy products i.e. gasolinel jet fuel and heating oil Oil produces more energy than same amount of Coal.
Natural gas is often a by product of oil.it is the mixture of gases the most common of whihc is methane. The main advantages of natural gas is that it is easy to tranport.
Most of the energy that we use comes from fossil fuels which are burned in power stations, factories, homes and vehicles etc. It is consumed in more than 80% of the world demand for energy.The disadvantages is that burning of fossil fuels caused atmospheric pollution.
Question: 6
Derivation of Gravitational Potential Energy.
Answer: 6
6-26
Question: 7
State the law of conservation of energy and mass energy conversion relation.
Answer: 7
7-26
Law of Conservation of Energy: "Energy can netigher be created nor destroyed in any process. It can be converted from one from to another bu the total amount of energy remains constnat".
Question: 8
Define Solar Energy
Answer: 8
8-26
Solar Energy: Solar energy is the energy obtained from sunlight. The energy from direct sun light can be used to produce electricity. Today Solar cells are used to power everything from calculators and watches to small cities. The energy obtained from sunliht is 100% free and very eco-friendly. It doesn't cause any pollution. BHowever, just like wind energy. huge land area is required to produce electricity.
Question: 9
Derivation of formula of Kinetic Energy
Answer: 9
9-26
Question: 10
What is potential Energy?
Answer: 10
10-26
Potential Energy: The energy possessed by a body due to its position or configuration in a force field is called potential energy.
Explanation: Potential energy can be produed by changing the position of a body horizontally or vertically that is said to elastic potential energy . For example, doing work on an ellastic band by stretching it stores potential energy in the elastic bond. also a battery contains both chemicla and electrical potential energy. When an object raised above the ground, it has gravitational potential energy due to its raised position.
Question: 11
Mathematical form of Kinetic energy. and unit
Answer: 11
11-26
Mathematical form: Mathematical kinetic energy is one half the product of an object mass "m" and the square of its velocity "v"
Ek = 1.2 mv2
unit: Kinetic energy is a scalar quantity and the SI unit of " Ek" is Joule.
Question: 12
Define Kinetic Energy .
Answer: 12
12-26
Kinetic Energy: The energy possessed by a body due to its motion is called kinetic energy.
Example:
1- Blowing wind
2- Moving car or train
3- Flowing water etc.
2-
Question: 13
Define Bio-mass
Answer: 13
13-26
"Bio" means life so bio-mass is the energy from living things, The term "bio mass" refers to the material from which we get bio-energy . Biomass is produced when the sun's solar energy is converted into plant matter by the process of photsynthetic. Only green plantsand photosynthetic algae, containing chlorophyll. are able to use solcar energy.The simplest process employed to make use of this energy is eating in this way, we are taking advantages of the energy stored as biomass.
Question: 14
Define Potential energy.
Answer: 14
14-26
The energy possessed by a body due to the position arrangement or state of the object is called potential energy. It is the energy that is stored in an objet that has potential to do work.So, when the position, arrangement or state of the object changes,the stored energy will be released. For example, chemicla potential energy is stored in the food you eat or the energy stored in stretced elastic band.
Question: 15
Define Heat Energy.
Answer: 15
15-26
Heat Energy: Heat energy is also known as thermal energy. Heat is a transfer of energy from one part of a substance to another or from one object to another due to difference in temperature. For example, burning of firetransfer the energy to keep room warm.
Question: 16
Define and explain Power.
Answer: 16
16-26
Power: Power isdefined as the time rate at which work is done or time rate at which energy is converted.
Mathematical form:
Mathematical ,Power can be written as.
Power = work /time
P = W/t
Or
Power = energy /time
P =E/t
Explaination: As we know power is a mwasure of how fast work is done or how fast energy is being converted from one form to another, Let suppose, there are two persons 'A' and 'B'. They both are having equal masses. Person 'A' runs 5 metersin 1 min while person 'B' also runs 5 meter in 3 mins. So it because bothe have shows that person 'A' is more powerful person 'B' than person 'B' because both have performed the sme work but person 'A' takes less time to cover a discnec of 5 m than person 'B' and he has peformed work faster than 'B' . Also his energy is quickly coverted fro one form to another. So, we relate work or energy with time which shows how much power power is consumedin given time period.
Quantity and Unit:
Power is a scalar quantity. The SI unit of power is watt where as I watt is equal to 1 Joule per 1 second i.e. 1 W = 1 J s-1

Question: 17
Define Chemical Energy
Answer: 17
17-26
Chemcial Energy: Chemicalenergy is the stored energy in the bonds of chemicla compounds such as atoms and molecules, These bonds can take many different forms,like it is the energy stored in food, gasoline in chemical combination, For example, striking a match stick or breaking light sticks releases chemical energy.
Question: 18
Define Energy and Unit of energy.
Answer: 18
18-26
Energy: Energy is defined as the ability to do work.
SI Unit: The SI unit of energy is Joule
Question: 19
Define Kinetic Energy.
Answer: 19
19-26
Kineti Energy: The energy possessed y a body due to its motion is called kinetic energy. if an object is moving, it has kinetic energy i.e. person running, a river flowing, or a car traveling on a road are the examples of kinetic energy.
Question: 20
Write Example of Efficiency.
Answer: 20
20-26
Example:
1- In light bulb 5% of the electricla energy transforms into light energy while the rest of given energy is wasted in the form of heat energy . So we,say, the efficiency of light bulb is only 5% out of 100%
2- If a petrol engine does 25 Joule of useful work for every 100 Jule of energy suppilied to it. then its efficiency will be 25%
Question: 21
Define and Explain efficiency.
Answer: 21
21-26
Efficiency: Efficiency is he ratio of useful energy or work output to the total energy or work input.
Mathematical form:
Efficiency = useful output work/ input work
Efficiency = Wo/Wi
Efficiency= useful energy output/ energy input
Efficiency= Eo/Ei
Percentage Efficiency:
Efficiency is always expressed in percentage It is defined as the ratio of useful energy provided by a devie to the energy requried to operate the device or mahine Mathemcatically th epercantage efficiency is calculate das follow.
Efficieicney = Eo /E1 x 100%
Efficiency = Wo/Wi x 100 %
Efficiency has not unit.


Question: 22
Define Nuclear Energy.
Answer: 22
22-26
Nuclear fission is the process of splitting large atoms i.e. uranium into two or more pieces, which release a huge amount of energy in the form of radiation of heat. The heat is used to boil water that is further used to produce electricity, In nuclear reactor small quantities of fuel produce large amount of energy .The advante is tha tmajor portionof heat energy is used for useful purpose while some part of energy is wasted that can cause pollutionand it is harmful for the mumans.
Question: 23
Define Electrical Energy
Answer: 23
23-26
Electrical Energy: The energy produed by electons moving through a substances is called electrcial energy. We mostly see electric energy in batteries and from the outless in our homes. It lights our homes, and runs all our appliances. Electrical energy is major source of energy that is used in hoes, offices,schools, industries etc.
Question: 24
Define Sound Energy.
Answer: 24
24-26
Sound Energy: Sound energy is produced when an object is made to vibrte Sound energy travels out as waves in all directions, Sound needs a medium to travel through such as air, water. Woods etc. For example, Voices, Whistles, horns and msical instruments produced sound energy.
Question: 25
Define Geo thermal energy.
Answer: 25
25-26
Geo means"earth" and thermal means "heat" , So, geo thermal energy is the heat energy obtained from earth's core. The thermal energy contained within Erah's core result from energy trapped almost 5 billion yars ago during the formation of planets. It is a natural renewable resources and doesn't cause any pollution. In many countries. geo thermal energy is used to generate electricity.
Question: 26
Define Radiant Energy.
Answer: 26
26-26
Radiant Energy is a combination of heat and light energy. It travels as an electromagnetic wave, Light energy like sound energy travels in all direction in waves, For example The microwavs cooks food on the basis of radiant energy. Other examples of radiant energy are teh glowing coils on a toaster, the sun and even headlights on cars.